I've heard repeatedly that Donald Trump is the front-runner for the Republican party presidential primaries when measured by polling for preferred candidate of republican voters, and Wikipedia backs that claim up.
However, I suspect that Donald Trump may not win the primaries, because while he has a large number of people who are strongly favourable to him, there's an even larger number of people who are strongly unfavourable to him.
I suspect that if polling measured what proportion of party voters had an overall positive, neutral, or only mildly negative attitude towards a given candidate, Trump wouldn't fare as well as other candidates.
My question is: Is polling for a party member's number 1 favourite candidate a useful way of predicting how likely a candidate is to win the primary? If not, what other polling is publicly available that can predict how likely a candidate is of winning the primary?
(Note: I'm not trying to ask who will win the Republican primary - I think that as of October 2015, the field is far too open to make predictions)